/   Home   /   Newsroom   /   Research News

Scientists Reveal Pacific North Equatorial Countercurrent Weak Biases in Ocean Models

Mar 04, 2019     Email"> PrintText Size

The Pacific North Equatorial Countercurrent (NECC) is a major upper-ocean zonal flow of the wind-driven circulation in the tropical Pacific, flowing eastward across the Pacific Ocean basin between 2°N and 10°N. The NECC transport is about 10–30 Sv eastward out of the warm pool region to the relatively cold eastern Pacific on average. It plays important roles in the volume and heat budget of the warm pool and in shaping the tropical Pacific climate. 

"The NECC is not well simulated in many ocean models because of its complex dynamics," said SUN Zhikuo, a Ph.D. candidate in the State Key Laboratory of Numerical Modeling for Atmospheric Sciences and Geophysical Fluid (LASG), Institute of Atmospheric Physics (IAP), Chinese Academy of Sciences.

In the recent second phase of the Coordinated Ocean-ice Reference Experiments (CORE-II), the NECC simulated in the stand-alone ocean models tend to be weak generally. This problem still exists in the Ocean Model Comparison Program (OMIP) of CMIP6.

"Weak NECC biases will affect the simulation ability of the average status and variability of the tropical surface currents," according to SUN.

In a recent study published in Journal of Advances in Modeling Earth Systems, SUN  and her supervisor Prof. LIU Hailong, in cooperation with researchers at Taiwan University and NCAR in the United States, systematically investigated the fundamental causes for the biases.

The team launched three experiments using Community Earth System Model version 2(CESM2) developed at NCAR and then analyzed the dynamic mechanism of NECC.


The upper 400 m vertically integrated zonal currents (Units: m2s-1) for (a) POP with CORE-II forcing, and (b) CESM in the equatorial Pacific. (c) The upper 400 m vertically integrated zonal current difference between CESM and POP. (d) The volume transports of NECC (Unit: Sv), which are defined as the meridionally integrated eastward transport between 3°N-10°N, for POP forced with CORE-II (red solid), CESM (blue solid) and Johnson et al. (2002) observation (black dots). The transports of the NECC masked by the observational sampling are also computed for both POP (red dash) and CESM (blue dash), donated as POP-J and CESM-J. (Image by SUN Zhikuo) 

"We found the surface wind stress and its curl is the most important forcing term for correctly simulating the NECC in ocean models. The WSC (wind stress curl) biases come mainly from the zonal wind bias, which may in turn relate to the adjustment of actual 10m winds in NCEP-NCAR reanalysis towards satellite equivalent 10m neutral wind from QuikSCAT," SUN said.

Based on the analysis, SUN and her coauthors further identified possible specific causes of wind biases. The problem may arise from the biases in QuikSCAT produce, or misusing of it. Now, they are focusing on the latter, in which the effect of the ocean currents on the computation of momentum flux has been accounted twice during the correction.

"This work provides clues to correcting the common biases of the climate and ocean models. It is expected to effectively improve the simulation ability of the tropical upper circulation in the stand-alone ocean models and reduce the impact of model deviation on climate simulation and prediction," LIU said. According to him, the work of correcting the biases in the climate ocean models is underway.

(Editor: LI Yuan)

Related Articles

wind erosion;simulation;coupled wind-erosion land-surface model;WEPS;Noah-MP; QInghai-Tibet Railway

Scientists Simulate the Wind Erosion along the Qinghai-Tibet Railway

Apr 28, 2018

Wind erosion along the Qinghai-Tibet Railway causes sand hazard and poses threats to the safety of trains and passengers. Acoupled land-surface erosion model (NOAH-MPWE0 was developed to simulate the wind erosion along the railway.

Jiaolong;South China Sea;dive;simulation

Chinese Submersible Jiaolong Tested Ahead of South China Sea Dive

Apr 25, 2017

Jiaolong, China's manned submersible, went through a dive simulation in Sanya, Hainan Province on Saturday to prepare for a deep descent in the South China Sea. The submersible stayed underwater for 18 minutes in Saturday's drill before returning Xiang...

acoustic logging while drilling; new typed receiver; receiving sensitivity response; simulation

New Acoustic Logging While Drilling Receiver Simulated with Small Size and Broad Frequency Band

Jan 26, 2015

Researchers from the State Key Laboratory of Acoustics, Institute of Acoustics of the Chinese Academy of Sciences simulate a new typed receiver with cavity structure composed by a bi-laminated piezoelectric bender and a hollow cylindrical shell. The ad...

Contact Us

Copyright © 2002 - Chinese Academy of Sciences